To read bar codes, use is usually made of an exclusive optical scanner, and in that case, an He-Ne laser, semiconductor laser or LED is used, the wavelength of light from these elements is in the range of 6000 .ANG. to 8000 .ANG..
Some bar codes are used for control of articles on the part of a manufacturer or wholesale section in the course of circulation of articles, while others are used for sales control at the stage of retail of the same articles. Thus, in many cases, each article has attached thereto a plurality of bar code labels to be read individually on different occasions.
In the case where a plurality of bar code labels are attached to each article, the location of application of each label is predetermined and an apparatus is used for controlling its relative position with the bar code reader, in order to automatically select and read one of said labels.